The invention relates to an inkjet printer for ejecting ink onto a recording medium made of a fiber structure to form images on the recording medium, and more particularly to an inkjet printer equipped with means for cleaning the surface of supporting means for supporting the recording medium.
At present, an attention has been made to an inkjet printing system, which can be used as a method for printing on a recording medium, such as a fibrous structure, by ejecting ink onto the recording medium to form images on it, from the textile industry for its effective application in small-lot multi-variety production.
The inkjet printing system is generally based on a printing mechanism, wherein a recording medium is held onto the surface of supporting means by adhesive or other similar means and is conveyed to a specified position; and ink is ejected or discharged from an inkjet head onto the recording medium for printing. If the recording medium is a thin cloth, net or other similar fabric, ink penetrates through the fabric to stain the supporting device, resulting in staining the fabric itself.
In addition, when ink is applied to the recording medium, such as fabric, the inkjet printing system requires the fabric to be securely stuck or adhered onto the surface of the supporting device during the ink ejection process. Therefore, when any fluff, yarn and other debris is left onto the surface of the supporting means or belt, the fabric may fail to stick securely onto the supporting device at the position where the debris is present. As a result, the fabric raises at the affected portion, causing the printing of the fabric to become uneven.
For the above-described reasons, the conventional printing machine, such as flat screen printing and rotary screen printing machines, for the recording medium with a fiber structure, in which the supporting means is provided to convey the recording medium stuck onto the surface thereof during the printing process, is normally equipped with a device as illustrated in FIG. 4 for cleaning the surface of the supporting means after detachment of the recording medium therefrom.
In FIG. 4, this cleaning device is designed to clean means for supporting the recording medium represented as an endless belt 30. The belt 30 is sprayed with water from a cleaning water injection nozzle 31, and is then contacted with a plurality of cleaning brush rolls 32 for removal of any residues deposited onto belt 30, such as color paste, fluff and yarn. Then, water left on the belt 30 is removed by scraping with a rubber doctor blade 33, and the belt 30 passes between press rolls 34 for further removal of water left on the belt 30 to clean the belt 30 and restore the stickiness on the surface thereof to its original state.
On the other hand, as disclosed in Japanese Patent Publication (KOKAI) No. 11-192694, there is an inkjet printer with cleaning means proposed for application in printing a recording medium with a fiber structure. This prior art inkjet printer is formed of a conveyer unit comprising means for supporting and conveying a recording medium as an endless belt, and means for driving the belt; a printing unit comprising an inkjet print head for injecting ink onto the recording medium conveyed by the endless belt; a recovery unit where the printed recording medium conveyed by the endless belt from the printing unit is detached from the endless belt for recovery; and a cleaning unit for washing the endless belt after the detachment of the recording medium therefrom in the recovery unit. The cleaning unit has a wiping roller, the surface of which is at least made of a porous polymer.
As one of the features, the above publication points out that the cleaning unit, because it has a wiping roll, the surface of which is at least composed of a porous polymer, is capable of removing water left on the endless belt together with any residue deposited thereon derived from the recording medium during the printing process, and that the wiping roll need not be replaced on a periodic basis.
According to the description of the above publication, however, the wiping roller is rotated while the porous polymer surface of the roller is pressed against the endless belt only for rubbing the belt in its conveying direction. This suggests that the wiping roller may have a sufficient force to scrape off any liquid material left on the belt such as water and ink, but not to remove any solid material stuck onto the belt, such as dust and yarn derived from the recording medium.
In addition, the wiping roller of such a sort as proposed in the above prior art must have a width enough to cover the width of the endless belt, so that the diameter thereof must be enlarged to a considerable extent, thus requiring a large space for its installation. This may promote to design a wiping roller of a similar type with its width and diameter both reduced, which, however, only results in providing more than one roller on the endless belt in its conveying direction, resulting in requiring a large space in that direction.
Eventually, the above-mentioned prior art cleaning unit has a disadvantage that it uses a large amount of water for cleaning the belt and requires its equipment, such as a brush for such cleaning, to be enlarged in size and using a large space for installation of the equipment, which, in turn, causes problems with its cost and maintenance.
The invention disclosed herein has been made to solve the above-mentioned problems involved in the prior art, and it is an object of the present invention to provide an inkjet printer, not only excellent in cost and maintenance, but also compact in structure, which is designed to ensure secure removal of any residues left on a belt for supporting a recording medium, such as fluff and yarn derived from the recording medium.
It is another object of the invention to provide an inkjet printer as stated above, which can assure stabilized quality of the resultant printed goods.
Further objects and advantages of the invention will be apparent from the following description of the invention.
Specifically, the present invention provides an inkjet printer comprising supporting means designed to convey a recording medium as stuck onto the surface thereof, printing means for ejecting ink onto the recording medium stuck onto the surface of the supporting means, and cleaning means for washing the surface of the supporting means after detachment of the recording medium therefrom. The cleaning means has suction means for drawing any residues left on the surface of the supporting means after the washing for removal of the residues.
In addition, the inkjet printer of the present invention has the following features.
The cleaning means is capable of moving or reciprocating back and forth in a direction perpendicular to or diagonal to the direction in which the supporting means is conveyed.
The cleaning means is also equipped with a brush for cleaning the surface of the supporting means and a nozzle for supplying a cleaning solution to the brush.
The cleaning means may be equipped with a porous structure for cleaning the surface of the supporting means and a nozzle for supplying a cleaning solution to the porous structure.
The cleaning means may be equipped with a fibrous structure for cleaning the surface of the supporting means and a nozzle for supplying a cleaning solution to the fibrous structure.
The suction means is located downstream of the cleaning means relative to the moving direction of the supporting means in such a way that the tip of the suction nozzle of the suction means faces the surface of the supporting means.
The cleaning means moves back and forth across the supporting means at a speed of 10 to 100 mm/sec.
The cleaning means according to the present invention is equipped with the suction means designed to securely remove any residues on the surface of the supporting means after the detachment of the recording medium, such as the fibrous structure therefrom, including not only liquid materials, such as printing ink and cleaning water, but also solid materials, such as fluff, yarn and dust, derived from the recording medium. In addition, because of the suction means provided as one of the features, the cleaning means has an advantage over the wiping roller type cleaning device described herein earlier as prior art in that it requires less periodic replacement, less installation space and far less maintenance, as well as no contact with the adhesive layer of the supporting means, causing far less damage to it.
According to the present invention, the cleaning means is equipped with a cleaning brush to apply physical brushing onto the supporting means by moving back and force in the direction perpendicular or diagonal to the direction in which the supporting means is conveyed. The brush moving direction, however, is preferably perpendicular to the supporting means conveying direction for the following reason.
The supporting means according to the present invention is coated with a sticky layer on its surface by a publicly known adhesive agent or sheet, such as based on a water-soluble, pressure-sensitive resin or heat-sensitive resin, to cause the recording medium, such as fabric, to stick securely onto the surface of the supporting means while the recording medium is printed.
During the inkjet printing process, the supporting means is subjected to repeated attachment and detachment of the recording medium, causing the surface of its sticky layer to become irregular with the depressed portions of the irregular sticky layer surface resultantly liable to collect liquid material, such as the ink penetrated through the recording material. The removal of the liquid material collected in such depressed portions of the sticky layer, as discovered by the inventor of the present invention, can be achieved more efficiently with a smaller amount of a cleaning solution by applying the brushing operation on the supporting means in the same direction as the inkjet head is scanned, that is, in the widthwise direction of the supporting means, rather than in its longitudinal direction as proposed in the prior art. In addition, the direction of moving the brush as proposed in the present invention is advantageous in that it only requires a relatively small stroke to push the solid materials left on the supporting means, such as fluff and yarn waste, from its center to its both ends.
According to the present invention, the cleaning means is not limited only to a brush as conventionally used for such cleaning, but can include a porous structure or fibrous structure such as cloth, which is to be selected properly according the type of the fabric to be printed as a recording medium, the cleaning condition to be applied and other factors to be considered in the inkjet printing process.
The suction means provided in the cleaning means according to the present invention preferably has the tip of its suction nozzle facing the surface of the supporting means at a position adequately adjusted to make a small gap therebetween.
According to the present invention, the adjustment of the gap between the tip of the suction nozzle of the suction means and the supporting means to be small allows suction air in the gap to have an increased velocity, thereby causing the cleaning solution to become atomized in a finer state to allow it to be more easily drawn into the suction nozzle for its removal. Experiments for the present invention have shown that the gap between the tip of the suction nozzle and the supporting means can be preferably set in the range of 0.2 to 5.0 mm.
As described above, the cleaning means of the present invention is designed to minimize the deterioration in the stickiness of the sticky layer on the surface of the supporting to means and to allow secure removal of any residues left on the supporting means after the detachment of the recording medium therefrom, including not only liquid materials, such as the ink and cleaning water waste, but also solid materials, such as fluff, yarn and dust, constituting the greatest problem in inkjet printing, thereby restoring the stickiness of the supporting means to make its surface condition proper for the next attachment of the recording medium.